A deciduous tree 20 to 30 ft high, with quite glabrous young shoots. Leaves ovate, coarsely toothed, sometimes lobed, 2 to 31⁄2 in. long, two-thirds as wide, the apex long-pointed, the base tapering, covered with fine down beneath, and with tufts of whitish hairs in the vein-axils. Flowers yellow, the males three or five together in short corymbs, the females in short slender racemes, appearing with the leaves. Fruit glabrous; keys 1 to 11⁄2 in. long; wings 1⁄4 to 1⁄2 in. wide, diverging at an angle of about 60°.
A. tetramerum is founded on a specimen collected by Henry in Hupeh but has a wide range in E. Asia from Kansu and Shensi to Upper Burma and S.E. Tibet. Even within a limited area it varies in the shape and indentation of the leaves and in the degree of downiness of the undersides and a number of varieties have been made out of these differences. These are, however, not very clearly demarcated from each other or from the type and it is best to distinguish the various cultivated forms by their original collectors' numbers, where these are still known, rather than by a varietal epithet.
Wilson introduced this species on his first expedition to China in 1901, under W. 680, collected in Hupeh; this is the form originally distributed by Veitch. In 1910 he sent seed from W. Szechwan under W. 4102 and probably most of the trees labelled var. betulifolium are from this number. The species is also in cultivation from seed collected by Forrest (F. 30462, 30625, 29396 and 28596), but these forms are rarer than Wilson's in gardens.
A. tetramerum is a very elegant maple, decorative in winter with its reddish to purplish young stems which later become green and striated after the fashion of the snake-bark maples. It is, however, quite distinct from these botanically and is more closely allied to A. argutum, being, like it, a dioecious species.
There are a number of good specimens at Westonbirt. The largest are in Clay Island and Victory Glade, both on two stems and about 40 ft high. Forrest's 30462 is represented by two small trees in Mitchell Drive and others in Silkwood. A tree at Caerhays Castle, Cornwall, probably raised from W. 4102, is 32 ft high, on several stems.
A. stachyophyllum Hiern – A small tree, closely related to the preceding, native of the E. Himalaya, Upper Burma, and parts of W. and S.W. China. Leaves ovate, with unlobed doubly serrate margins and a long, curving tip, downy beneath. Fruits larger than in A. tetramerum and the racemes often branched; in cultivation from Kingdon Ward 10965 and Forrest 11252. This species is rare in gardens but is quite hardy in woodland at Borde Hill, Sussex, and is represented at Edinburgh by four specimens, the tallest 25 ft high. In his Field Notes, Kingdon Ward records that in the Zayul region of the E. Himalaya 'drinking cups are made from its wood – the most expensive kind'.
The boundary between this species and A. tetramerum appears to be rather uncertain.
From the Supplement (Vol. V)
specimens: Wakehurst Place, Sussex, 35 × 33⁄4 ft (1981); R.H.S. Garden, Wisley, Surrey, on Battleston Hill, 65 × 31⁄4 ft (1981); Westonbirt, Glos., a many-stemmed tree 48 ft high (1978); Edinburgh Botanic Garden, 31 × 31⁄2 ft (1981).
It is doubtful whether A. tetramerum is really distinct enough from A. stachyophyllum, named much earlier, to rank even as a subspecies.